4.2 on J720

people are saying it can be done with a J728. So can it be done with a J720?

the hardware is pretty much exactly the same - the rom board that we're talking of replacing contains the RAM too so a 720 could be upgraded at the same time

As for whether it can be done, well, if you can make it go on the 728 then it'll work on the 720 as well. Whether it'll ever happen is a completely different subject

But in theory, with the right drivers, enough commitment, a new flash board and a following wind, it could work.

cool!

What exactly is the difference between a J720 and a J728?

(what would happen if I just coped the 4.2 files onto my /windows folder on my handheld?

Ah, there's the rub.

The operating system is locked onto a Read Only Memory chip in the J720. It cannot be written to or copied from. If you try to copy system files, the device will tell you "no way". What is intriguing about this project is that they are trying to come up with a way to put (or acquire) CE4.2 on a new chip and replace the chip on the J720 entirely (an oversimplification of the undertaking, but that seems to be the meat of it). Now there's all sorts of special software needed to be written so the 4.2 OS can interact with all the hardware on the device: screen, keyboard, drives, etc. since it wasn't ever meant to be on the Jornada.

If I am following the proceedings correctly, there is another theory that you can run the CE4.2 OS ontop of the CE3.0, kind of like the Linux OS camp has done. This wouldn't require a physical chip swap, but getting the device to boot to software other than what is on the chip is the issue, as well as performance/memory limitations, I believe (oh, and the device drivers would still need to be custom made).

Anyone: feel free to correct me if I'm wrong, but those are my impressions. I hope they can make it work. I'd be willing to spend money on the upgrade.


Edited by PDAfan 2006-11-17 12:04 PM

Nope, that's pretty much the heart of it. We need experienced programmers and anyone who has made successful use of Platform Builder.

Edited: cause I don't spell good.

Edited by oflash 2006-11-17 12:42 PM

yes as soon as we find programmers experienced in win32 driver writing (even better if CE drivers) our chances increase a lot. if this helps, i'm willing to lend a jornada 720 to them.

Just curious - buy why stop at 4.2? If you are going to use PBuilder to build a ROM image for a new "flashboard", why not go with 5.0, or even 6.0?

Since MS announced CE 6.0, and the kernel source, seems you could create a 6.0 platform (size, etc., issues maybe). Yeah, I don't have driver source - but that's no mystery between netbsd and linux distros for the J72x.

Agreed, the PBuilder cost for 6.0 seems to be about $1000USD, but I've checked other PB (3.0, etc.), and they ain't too cheap either. Also, the 6.0 PB can be downloaded and used for free for 6 months (to test validity of project), before you have to buy it - or you buy it when you start selling product.

I have no idea what the licensing cost would be for 6.0 - but you surely can't think you are going to deliver 4.2 ROM images for the J72x without paying MS something, or running afoul of the PB EULA ?!?!?!?!?

because I think that the CE4.2 is the one that best fits on the jornada specs of screen, keyboard, etc etc

Extracting the whole image is not difficult if you've got access to flash tools for the PocketPC (try xda-developers.com), some programming skills - though admittedly low level knowledge of computer hardware basics is needed too - and most importantly time that you can commit to reading the ROM.

I've got two out of three, but being honest I just don't have the time, and again being honest the 720 is not the ideal device for me because of the awful screen.

Someone should be able to take the work done by xfadevelopers or others and make it work on the 720. Sorry that this isn't an offer to do it for you, but I really do not have the time that this would need or passion to achieve the end goal.

So, who on the boards is capable of this sort of thing?

To address the CE 5.0 and 6.0 question: Word has it that 4.2 was the last build that supports the Jornada's Strong Arm processor, the SA1110. Modern Xscale processors, like the PXA255 in the 900c and many others, can run the older software, but the older hardware can't run the newer software.

It's the old backwards/frontwards compatibility thing. Think of it as trying to run modern Windows on a 386 chip.

I'll not mention the matter of licensing either, shall I?

Please bear in mind that 5 and 6, and 4.2, will all need licensing to be worked out somehow. These OSes are emphatically not free.

about 5.0 or 6.0, you'll need some support for the strongarm, ask mullenger (simpad 4.2 OS maker) if he found a solution... last time i checked he didn't.

if everyone builds their own bin file (OS image ready to be flashed) everyone can flash it on their device for free. that is not in breach of the 4.2 evaluation edition EULA

anyway the licensing cost shouldn't be too high, but we would need enough interested buyers for that.

PB 3.0 cost 150$ for C:Amie.

dumprom of course will extract the image, we've known that. good enough to disassemble the stuff - though i don't know how much we'd need of that (ask the linux guys). not good for anything else without further modifications.
xdadev stuff doesn't give us anything to write drivers. (other than the disassembly) so not sure i'm following you there.

hehe, don't tell me you have the low level knowledge AND you won't work on this
btw, "awful screen" - that's subjective, i don't think it is awful but i understand you're not interested. too bad really

so if it was possible to copy the files over to the rom chip we could, However its read only so we cant? so what would happen if it was writen to a cf card and booted like linux. that would work?

There are no "the files". You need drivers too. They don't exist yet. (I personally won't be holding my breath either.)

As for booting, without replacing the ROM, there would need to be a bootloader that loads a RAM OS. I'm not sure whether CE 4.2 has an option to run with the CF being the filesystem root.

Edited by isotherm 2006-11-17 6:32 PM